The glycopeptide, or vancomycin, class of antibiotics are crystalline, amphoteric, strongly laevorotatory compounds of relatively high molecular weight. Structurally, they comprise a polypeptide core aglycone structure having phenolic amino acids and one or more peripheral carbohydrate moieties. See, Williams et al., Topics in Antibiotic Chemistry, Volume 5, pages 119-158. Known members of this class include vancomycin (McCormick et al., U.S. Pat. No. 3,067,099), ristocetin (Philip et al., U.S. Pat. No. 2,990,329), A35512 (Michel et al., U.S. Pat. No. 4,083,964), avoparcin (Kunstmann et al., U.S. Pat. No. 3,338,786) teicoplanin (Bardone et al., J. Antibiot., Volume 31, page 170, 1978), actaplanin (Raun, U.S. Pat. No. 3,816,618), AAD-216 (Bowie et al., EP-A No. 132118), A477 (Raun et al., U.S. Pat. No. 3,928,571), OA7633 (Nishida et al., U.S. Pat. No. 4,378,348), AM 374 (Kunstmann et al., U.S. Pat. No. 3,803,306), K288 (J. Antibiotics, Series A, Volume 14, page 141 (1961), also known as actinoidin).
The glycopeptide antibiotics exhibit antibacterial activity, some having therapeutic uses against gram-positive organisms. In addition, many have been demonstrated to increase animal feed utilization efficiency and, therefore, to be useful to promote animal growth, to improve milk production in ruminants and to treat and to prevent ketosis in ruminants. For example, Reynolds et al., GB No. 2137087A, disclose use of avoparcin to improve milk production; Raun et al., U.S. Pat. No. 3,928,571 disclose use of actaplanin, avoparcin (A477), vancomycin and ristocetin to promote growth and to prevent and to treat ketosis; Hamill et al., U.S. Pat. No. 3,952,095, disclose use of actaplanin to promote growth; and Ingle et al., U.S. Pat. No. 4,206,203 disclose use of avoparcin to prevent and to treat ketosis.